144 Dr. J. H. Gladstone. The Relation between the 



Trivalent Metals. 



The trivalents proper and arsenic agree still more closely amongst 

 themselves, and give a mean of 1*01, which is practically identical 

 with that of the bivalents proper. 



The other trivalents, which have well-marked higher valencies, 

 exhibit, as before, a somewhat higher product. 



Quadrivalent Metals. 



In this case the mean is 1*06, nearly the same as with the bivalents 

 arid trivalents, but the numbers are not so regular. 



We have observations on one pentad, namely, antimony. This 

 gives- 

 Specific refractive energy 0*200 



^Combining proportion 4'9 



Product 0-98 



These tables show : First, that the metals which have the same 

 valency, have the same, or nearly the same, constant of refraction 

 for equivalent weights. 



